The overall goal of this proposal is to immunomodulate tumor cells with monoclonal antibody (MAb) genes for therapy of human cancer. Preliminary studies have demonstrated that a human colon tumor cell line can produce self-reactive antibody following retrovirus-mediated transfer of murine MAb genes, and that these MAb gene-transduced tumor cells display altered tumorigenicity in vivo. The MAb encoded by the latter genes can participate with NK/LAK cells and macrophages in mediating antibody- dependent cell mediated cytotoxicity (ADCC). Using these MAb gene- transduced human colon carcinoma cell lines, the first aim will determine if the latter cells as well as admixed non-transduced parental tumor cells are susceptible to killing in assays of ADCC. The tumorigenic properties of MAB-gene transduced tumor cells will be studied in athymic mice. The mechanisms for loss of transduced tumor cell tumorigenicity will be evaluated in athymic mice having suppressed NK cell or macrophage function. For the second aim, genetically engineered MAbs will be prepared having improved expression and effector function properties. Mouse/human chimeric IgG1 MAbs will be constructed to enhance ADCC. Single chain Fv MAbs will be prepared to facilitate MAb gene-transduction and expression. To determine the role that local targeting of FCR+ cells by MAbs has in provoking rejection mediated by MHC-restricted cytotoxic T-cells, the third aim will prepare transplantable, syngeneic murine colon tumor cells that express both a human tumor antigen, CEA, and an ADCC-mediating antibody against this antigen. The tumorigenicity of the cytotoxic MAb gene-transduced murine tumor cells will be studied in syngeneic hosts and their ability to elicit protection against non- transduced parental cells will be evaluated. These studies will explore the effectiveness of an ADCC-mediating antibody in promoting the development of CTLs through enhanced antigen presentation and/or cytokine release by effector cells such as macrophages and NK cells participating in ADCC reactions against MAb gene-transduced tumor cells. Selective induction of CTLs against alien antigens will be pursued by transduction of syngeneic tumors with genes encoding for foreign immunoglobulin heavy chains. The protective and therapeutic properties of a tumor cell vaccine genetically modified to express alien immunoglobulin antigens will be examined in animals bearing unmodified tumors cells. The planned studies will hopefully lead to a new immunotherapeutic approach for the treatment of cancer that is based on the ability of a MAb gene-transduced tumor cell vaccine to induce immunological responses against weak antigens that are unique and native to the tumor cell.